Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• the possibility for variations outside these complex sequences, for example the radical-induced 1,3-shift of a cinnamyl moiety, likely to occur at a point buried within the mechanistic mix illustrated in Scheme 9. Clearly, further mechanistic studies will be required to continue to explain the

A procedure for the preparation and isolation of nucleoside-5’-diphosphates

• Heidi J. Korhonen,
• Hannah L. Bolt and
• David R. W. Hodgson

Beilstein J. Org. Chem. 2015, 11, 469–472, doi:10.3762/bjoc.11.52

• synthesis; nucleic acids; nucleoside-5’-diphosphate; phosphorylation; Introduction Nucleoside-5'-phosphates are key to many mechanistic studies and chemical biology applications [1][2][3]. Synthetic approaches towards nucleoside-5'-phosphates are well-established [4], however, the methods tend to be

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• coupling catalysts [72]. The relatively low performance of WIDEPHOS, when operating as a bis(monodentate) ligand, is probably the result of the severe steric encumbrance generated within the cavity of the postulated dinuclear complex. According to a number of mechanistic studies, the structure of the

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• organic chemistry and biochemistry, but they are particularly important for mechanistic studies in biochemistry and biophysics [6][8][9][10][11]. Most PPG candidates require sufficiently high energy excited states for heterolysis of a carbon–oxygen or carbon–heteroatom bond that binds the chromophore to a

• attempted to circumvent or avoid the inherent deficiencies of the classical o-NB, benzoin, and coumaryl analogs (see Figure 1). A noisome limitation of o-NB PPGs that mitigate their general use in biological and mechanistic studies are their inherently slow reaction rates. o-NB rate constants are decidedly

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

• J. Alexander Willms,
• Rita Beel,
• Martin L. Schmidt,
• Christian Mundt and
• Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

• -ethylpyridinium-4-phenoxy substituent has been synthesized with the aim of facilitating mechanistic studies of proline-catalyzed reactions by ESI mass spectrometry. The charged residue ensures a strongly enhanced ESI response compared to neutral unmodified proline. The connection by a rigid linker fixes the

• as a function of time [8] and beyond that a characterization of transient intermediates by tandem mass spectrometry. ESI mass-spectrometric mechanistic studies have been reported for a broad range of reaction types ranging from transition metal-catalyzed polymerization [6][9] and coupling reactions

• , mechanistic studies on organocatalytic reactions [31][32][33][34][35][36][37][38] using ESI mass spectrometry [20][39][40][41][42][43][44][45][46][47][48][49] have been reported. The pioneering studies of List and Barbas [50] revealed that the amino acid L-proline is an effective catalyst for a great variety

Facile synthesis of 1-alkoxy-1H-benzo- and 7-azabenzotriazoles from peptide coupling agents, mechanistic studies, and synthetic applications

• Mahesh K. Lakshman,
• Manish K. Singh,
• Mukesh Kumar,
• Raghu Ram Chamala,
• Vijayender R. Yedulla,
• Domenick Wagner,
• Evan Leung,
• Lijia Yang,
• Asha Matin and
• Sadia Ahmad

Beilstein J. Org. Chem. 2014, 10, 1919–1932, doi:10.3762/bjoc.10.200

• mechanistic details would be required. Thus, the next stage in these investigations focused on this aspect. Mechanistic studies Our investigations began with the reactions of BOP. We reasoned that among the three pathways shown in Scheme 2, 31P{1H} NMR may allow for distinguishing pathway a from b and c. Thus

• alkyl halides or more cumbersome methods. Mechanistic studies indicate that reactions of alcohols with these peptide-coupling reagents, in the presence of a base, appear to proceed by formation of alcohol phosphonium derivatives (with BOP), or alcohol tosylates (with Bt-OTs), and not through direct

Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

• Marina Caporaso,
• Giancarlo Cravotto,
• Spyros Georgakopoulos,
• George Heropoulos,
• Katia Martina and
• Silvia Tagliapietra

Beilstein J. Org. Chem. 2014, 10, 1454–1461, doi:10.3762/bjoc.10.149

• esterification has not still been fully elucidated. Additional mechanistic studies will be needed to support a mechanistic rationale. Conclusion In summary, we have described a highly efficient, versatile and eco-friendly protocol for the aerobic esterification of benzylic alcohols and aldehydes to methyl esters

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• various applications of eosin Y to visible light-driven syntheses of biaryls [15], stilbenes [16], benzothiophenes [17], α-phenylketones [18], phenanthrenes [19], arylsulfides [20] and arylboron pinacolates [21] (Scheme 1). Numerous mechanistic studies have been performed at reactions with organometallic

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• an increase of radical in the solution. Conclusion In this paper experimental and full mechanistic studies of Type II PIS and 3-cpt photocatalytic systems were presented and compared. Some advantages that PCIS bear over classical Type II systems are: dye regeneration with high possible turnover (600

Multicomponent reactions II

• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 115–116, doi:10.3762/bjoc.10.7

• . Biologically active compounds and photonic properties are addressed as well as mechanistic studies and models. The interested reader – whether an expert in the field or a newcomer – will find exciting reports from the current realm of MCR chemistry. As the guest editor of this Thematic Series I cordially thank

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• understand the problems as to speciation and nuclearity faced by mechanistic studies. More general aspects of the CuAAC as well as the multitude of fields, in which this reaction has become essential, are highlighted in a great many of recommendable review articles [14][18][19][20][21][22][23][24][25][26][27

• and the lack of species that can compete with the substrates for free coordination sites at the copper(I) centre are probably the main factors why some complexes of type [(NHC)2Cu]X are catalytically more active than the [(NHC)CuX] family. Mechanistic studies Mononuclear mechanistic proposal In his

• consequence, they suggested two copper centres to be required for catalytic turnover. Mechanistic studies for the “ligand-free” CuAAC followed [160]. The reaction of benzyl azide with phenylacetylene in dimethyl sulfoxide/water in the presence of copper(II) sulfate pentahydrate and an excess of sodium

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• facilitate the reductive elimination step. However, the phosphine was changed for the less bulky ligand RuPhos for the reaction with ortho-substituted aryl chlorides. The authors presume a Pd(0)/Pd(II) catalytic cycle, which is supported by preliminary mechanistic studies. In 2011, B. S. Samant and G. W

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• [68]. The Wu group concurrently developed the Eosin Y-catalyzed aza-Henry reaction as reported by König and also performed mechanistic studies on the reaction. Their proposed catalytic cycle for the reaction is detailed in Scheme 6 [69]. Wu and coworkers were able to obtain experimental evidence to

• . Oxidative functionalization of N-aryltetrahydroisoquinolines using Eosin Y. Synthetic and mechanistic studies of Eosin Y-catalyzed aza-Henry reaction. Oxidative functionalization of N-aryltetrahydroisoquinolines using RB and GO. Merging Ru-based photoredox catalysis and Lewis base catalysis for the Mannich

Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

• Andreas Gansäuer,
• Meriam Seddiqzai,
• Tobias Dahmen,
• Rebecca Sure and
• Stefan Grimme

Beilstein J. Org. Chem. 2013, 9, 1620–1629, doi:10.3762/bjoc.9.185

• radical precursors [16][17][18][19][20]. Despite this usefulness only few studies have been concerned with the determination of absolute rate constants of radical additions to arenes. These were carried out in mechanistic studies of the Minisci reaction [21][22]. It was found that the butyl radical adds

Mechanistic studies on the CAN-mediated intramolecular cyclization of δ-aryl-β-dicarbonyl compounds

• Brian M. Casey,
• Dhandapani V. Sadasivam and
• Robert A. Flowers II

Beilstein J. Org. Chem. 2013, 9, 1472–1479, doi:10.3762/bjoc.9.167

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• homolytic substitution at phosphorus. The new tool for C–P bond formation has achieved interesting transformations that ionic reactions cannot. This review summarizes homolytic substitution at phosphorus for C–P bond formation in organic synthesis while the relevant mechanistic studies are found in the

• thiophosphination (Scheme 9). Detailed mechanistic studies revealed that comproportionation between PhSe–SePh and Ph2P–PPh2 occurs smoothly to generate PhSe–PPh2 as the actual reactive species. Selenophosphination of terminal allene affords (2-phenylselenyl-2-alkenyl)diphenylphosphine regioselectively (Scheme 11

Synthesis of SF₅-containing benzisoxazoles, quinolines, and quinazolines by the Davis reaction of nitro-(pentafluorosulfanyl)benzenes

• Petr Beier and
• Tereza Pastýříková

Beilstein J. Org. Chem. 2013, 9, 411–416, doi:10.3762/bjoc.9.43

• nitroarenes; and (c) substitution of hydrogen in ortho- or para-positions to the nitro group through vicarious or oxidative nucleophilic substitutions. Mechanistic studies have revealed that in all of these reaction pathways, the primary process is the reversible addition of nucleophiles to the ring carbon

Thioester derivatives of the natural product psammaplin A as potent histone deacetylase inhibitors

• Matthias G. J. Baud,
• Thomas Leiser,
• Vanessa Petrucci,
• Mekala Gunaratnam,
• Stephen Neidle,
• Franz-Josef Meyer-Almes and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2013, 9, 81–88, doi:10.3762/bjoc.9.11

• ), 9 was inactive against A549 and WI38 cells at the highest concentration tested (50 μM). Similar to our previously reported SAR and mechanistic studies, a correlation between HDAC inhibition and cytotoxicity is clearly observable for these psammaplin A prodrugs. Notably, in enzyme assays, the

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• , thus, gave data ideally suited to mechanistic studies [56]. The potential of microreactors in the photocatalytic splitting of water has also come under investigation. In this case a rhodium-containing inorganic photocatalyst was employed, and again online QMS permitted mechanistic studies to be

• conversion at the expense of increased dimer formation, both effects being ascribed to the greater average photon density in the flow system [70]. Mechanistic studies of the photoreduction of benzophenone (63) with benzhydrol (64) (Scheme 20) have been performed in a microflow reactor, allowing the quantum

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• , radical anion 25, a strong reducing agent, transfers one electron to starting iodobenzene and results in the formation of biphenyl, potassium iodide and phenyl radical (Scheme 17). However, the role of the organocatalyst is still not fully understood at this point and detailed mechanistic studies are

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• considered. Keywords: diradicals; mechanisms; photochemistry; Introduction Photoinduced ring-opening or ring-fragmentation processes constitute an important type of reaction in organic photochemistry and have been examined both from a mechanistic and a synthetic point of view [1][2][3][4][5]. Mechanistic

• studies have revealed information on reactive intermediates, solvent effects, and stereochemical outcomes, while synthetic work has pointed to novel approaches for preparing various molecules. For example, deazetation reactions in solvents of increasing viscosity were employed to determine whether the

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• mechanism is not well established. Several mechanistic studies have been performed on the isomerization reversal route cis→trans of azobenzene to investigate the effect of the substituents on the benzene rings as well as the influence of several parameters [24][25][26][27]. The available data suggest that

Bromine–lithium exchange: An efficient tool in the modular construction of biaryl ligands

• Laurence Bonnafoux,
• Frédéric R. Leroux and
• Françoise Colobert

Beilstein J. Org. Chem. 2011, 7, 1278–1287, doi:10.3762/bjoc.7.148

• method lacking both appeal and surprise [33], and only new applications of this reaction or mechanistic studies have been reported [30][32][33][45][46][47][48][49][50][51][52][53][54][55]. However, in the last few years, the halogen–metal permutation has recaptured its former role as one of the most